This 11-centimetre (4.3-inch) frog appears to have tufts of hair on its sides and thighs, but they are actually dermal papillae – fleshy outgrowths that contain arteries. They act to massively increase the skin surface area, which allows the hairy frog to absorb more oxygen when sitting underwater.
But it’s not just its ‘sideburns’ that make the hairy frog resemble X-Men’s Wolverine. It can also extrude sharp claws by intentionally forcing them through its skin. The spines are normally held in place with a ligament but, when threatened, the frog clenches its fist so forcefully that the ligaments snap and pierce its skin.
Unlike Wolverine, the spines can’t be actively retracted; they just ease back over time and the skin regrows over them.